netdev - [PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf

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Message-Id: <1747540070-11086-1-git-send-email-ssengar@linux.microsoft.com>
Date: Sat, 17 May 2025 20:47:50 -0700
From: Saurabh Sengar <ssengar@...ux.microsoft.com>
To: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com,
	horms@...nel.org,
	ast@...nel.org,
	daniel@...earbox.net,
	hawk@...nel.org,
	john.fastabend@...il.com,
	sdf@...ichev.me,
	kuniyu@...zon.com,
	ahmed.zaki@...el.com,
	aleksander.lobakin@...el.com,
	linux-hyperv@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org
Cc: ssengar@...rosoft.com,
	stable@...r.kernel.org,
	Saurabh Sengar <ssengar@...ux.microsoft.com>
Subject: [PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()

The MANA driver's probe registers netdevice via the following call chain:

mana_probe()
  register_netdev()
    register_netdevice()

register_netdevice() calls notifier callback for netvsc driver,
holding the netdev mutex via netdev_lock_ops().

Further this netvsc notifier callback end up attempting to acquire the
same lock again in dev_xdp_propagate() leading to deadlock.

netvsc_netdev_event()
  netvsc_vf_setxdp()
    dev_xdp_propagate()

This deadlock was not observed so far because net_shaper_ops was never
set and this lock in noop in this case. Fix this by using
netif_xdp_propagate instead of dev_xdp_propagate to avoid recursive
locking in this path.

This issue has not observed so far because net_shaper_ops was unset,
making the lock path effectively a no-op. To prevent recursive locking
and avoid this deadlock, replace dev_xdp_propagate() with
netif_xdp_propagate(), which does not acquire the lock again.

Also, clean up the unregistration path by removing unnecessary call to
netvsc_vf_setxdp(), since unregister_netdevice_many_notify() already
performs this cleanup via dev_xdp_uninstall.

Fixes: 97246d6d21c2 ("net: hold netdev instance lock during ndo_bpf")
Cc: stable@...r.kernel.org
Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
---
 drivers/net/hyperv/netvsc_bpf.c | 2 +-
 drivers/net/hyperv/netvsc_drv.c | 2 --
 net/core/dev.c                  | 1 +
 3 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c
index e01c5997a551..1dd3755d9e6d 100644
--- a/drivers/net/hyperv/netvsc_bpf.c
+++ b/drivers/net/hyperv/netvsc_bpf.c
@@ -183,7 +183,7 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog)
 	xdp.command = XDP_SETUP_PROG;
 	xdp.prog = prog;
 
-	ret = dev_xdp_propagate(vf_netdev, &xdp);
+	ret = netif_xdp_propagate(vf_netdev, &xdp);
 
 	if (ret && prog)
 		bpf_prog_put(prog);
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index d8b169ac0343..ee3aaf9c10e6 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -2462,8 +2462,6 @@ static int netvsc_unregister_vf(struct net_device *vf_netdev)
 
 	netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name);
 
-	netvsc_vf_setxdp(vf_netdev, NULL);
-
 	reinit_completion(&net_device_ctx->vf_add);
 	netdev_rx_handler_unregister(vf_netdev);
 	netdev_upper_dev_unlink(vf_netdev, ndev);
diff --git a/net/core/dev.c b/net/core/dev.c
index fccf2167b235..8c6c9d7fba26 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9953,6 +9953,7 @@ int netif_xdp_propagate(struct net_device *dev, struct netdev_bpf *bpf)
 
 	return dev->netdev_ops->ndo_bpf(dev, bpf);
 }
+EXPORT_SYMBOL_GPL(netif_xdp_propagate);
 
 u32 dev_xdp_prog_id(struct net_device *dev, enum bpf_xdp_mode mode)
 {
-- 
2.43.0